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Poster: hank_b Date: Apr 7, 2010 9:28pm
Forum: texts Subject: Re: Poor PDF quality

The full-book PDFs are intended to be a convenience more than a high-quality record of the item. In order to obtain a good compression ratio we had to make several compromises, and you are exactly correct that those compromises work to the detriment of photographs. Because so much of our material is text or line drawings or artwork with large blocks of constant color, we optimized for those kinds of images; photographs, with their fine gradations, do poorly.

But yes, there are alternatives to the PDFs:

Pages may be viewed individually via the Read Online link (the "BookReader"). When you zoom to 100%, what you're seeing is the full resolution of our master jpeg2000 images. URLs for specific pages and zoom levels can be bookmarked or otherwise saved. You can also extract the images themselves, without the BookReader skin, via URLs like:

http://{server}{path to jp2 zip}&file={file path within the jp2 zip}&scale={n}

or you can embed the BookReader on web pages of your own. You may find that a convenient way to view books you wish to "keep."

Alternatively, if you have the bandwidth, you can download the entire file from the directory listing that is accessed via the "All Files: HTTP" link. Once unzipped, that will give you a directory of full-resolution jpeg2000 images, one for each page in the book.

Another option is to try the DjVu file - like the PDFs, the DjVus are highly compressed, but because they use different compression algorithms, it's possible they'll do better with photos. Some browsers have plug-ins to view DjVu files; I've actually been pretty happy with the DjView standalone app.

Hank Bromley
Internet Archive

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Poster: Organoid Date: Apr 7, 2010 10:21pm
Forum: texts Subject: Re: Poor PDF quality

Thank you very much for the response. Your assistance has made my project workable. Much appreciated.